What is the treatment for polymyxin (antibiotic) otitis externa (outer ear infection)?

Treatment of Polymyxin Otitis Externa

Topical antimicrobial therapy is the mainstay of treatment for otitis externa caused by polymyxin-resistant bacteria, with quinolone ear drops being the preferred first-line option due to superior efficacy and safety compared to neomycin/polymyxin B combinations. 1, 2

First-Line Treatment

• Topical quinolone ear drops (ofloxacin or ciprofloxacin) are recommended as first-line therapy due to increasing resistance to polymyxin B and neomycin, and lack of ototoxicity risk 2, 1
• Ofloxacin otic solution once daily has demonstrated equivalent efficacy to neomycin/polymyxin B/hydrocortisone four times daily, with the advantage of less frequent dosing and no risk of ototoxicity 3
• Aural toilet (cleaning the ear canal) should be performed before administering drops to ensure medication reaches infected tissues 4, 1

Administration Technique

• Have the patient lie with the affected ear upward 4
• Administer enough drops to fill the ear canal 4
• Have the patient remain in this position for 3-5 minutes 4
• Use gentle to-and-fro movement of the pinna or tragal pumping to eliminate trapped air and ensure proper distribution 4, 5
• The ear canal should be cleared of inflammatory debris before administration 4

Pain Management

• Assess pain severity and recommend appropriate analgesics based on pain severity 4, 1
• Pain typically improves within 48-72 hours of starting appropriate topical therapy 1
• Continue analgesics as needed until pain resolves 4

Special Considerations

For Non-Intact Tympanic Membrane

• Avoid ototoxic preparations (including polymyxin B/neomycin) in patients with perforated tympanic membrane or tympanostomy tubes 1, 5
• Use non-ototoxic quinolone preparations (ofloxacin, ciprofloxacin) instead 1, 4

For High-Risk Patients

• Patients with diabetes, immunocompromised states, or history of radiotherapy require special consideration 1, 4
• Monitor these patients more carefully for signs of necrotizing otitis externa 1
• Consider systemic antibiotics in addition to topical therapy for these high-risk patients 1

When to Consider Systemic Antibiotics

• Systemic antibiotics should NOT be used as initial therapy for uncomplicated otitis externa 4, 1
• Reserve oral antibiotics for specific circumstances:
  • Extension of infection beyond the ear canal 4, 1
  • Patients with diabetes or immunocompromised status 1
  • When topical therapy cannot reach the infected area or has failed 1
  • Presence of cellulitis of the pinna or adjacent skin 4

Treatment Failure Considerations

• If no improvement occurs within 48-72 hours, consider: 1, 5
  • Inadequate drug delivery due to canal obstruction 1
  • Allergic contact dermatitis (especially to neomycin, which causes reactions in 5-15% of patients) 4, 5
  • Fungal co-infection requiring antifungal therapy 1, 5
  • Incorrect diagnosis 1

Emerging Resistance Concerns

• Studies have shown increasing minimum inhibitory concentrations (MICs) for polymyxin B and neomycin against common otitis externa pathogens 2
• In contrast, MICs for quinolones like ofloxacin have remained stable and within the susceptible range 2
• The bacterial eradication rates for neomycin/polymyxin B/hydrocortisone have been shown to be lower (87%) than for ofloxacin (93%) 2

Patient Education

• Instruct patients on proper administration technique 1
• Inform patients that symptoms typically improve within 48-72 hours 1, 5
• Advise patients to complete the full course of therapy even if symptoms resolve early 1
• Recommend keeping the ear dry during treatment 4
• Instruct patients to return for reassessment if symptoms don't improve within 48-72 hours 1